Mostly use entities in use.dart

tests/compiler/dart2js/kernel/impact_test.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.kernel.impact_test;
 
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/commandline_options.dart';
 import 'package:compiler/src/common.dart';
 import 'package:compiler/src/common/names.dart';
@@ skipping 691 matching lines @@
   ResolutionWorldImpactBuilder builder =
       new ResolutionWorldImpactBuilder('Lax impact of ${element}');
   for (StaticUse staticUse in impact.staticUses) {
     switch (staticUse.kind) {
       case StaticUseKind.CONSTRUCTOR_INVOKE:
       case StaticUseKind.CONST_CONSTRUCTOR_INVOKE:
         ConstructorElement constructor = staticUse.element;
         ConstructorElement effectiveTarget = constructor.effectiveTarget;
         ResolutionDartType effectiveTargetType =
             constructor.computeEffectiveTargetType(staticUse.type);
+        ConstructorElement effectiveTargetDeclaration =
+            effectiveTarget.declaration;
         builder.registerStaticUse(
             staticUse.kind == StaticUseKind.CONST_CONSTRUCTOR_INVOKE
                 ? new StaticUse.constConstructorInvoke(
-                    effectiveTarget.declaration, null, effectiveTargetType)
+                    effectiveTargetDeclaration, null, effectiveTargetType)
                 : new StaticUse.typedConstructorInvoke(
-                    effectiveTarget.declaration, null, effectiveTargetType));
+                    effectiveTargetDeclaration, null, effectiveTargetType));
         break;
       default:
         builder.registerStaticUse(staticUse);
         break;
     }
   }
   impact.dynamicUses.forEach(builder.registerDynamicUse);
   for (TypeUse typeUse in impact.typeUses) {
     builder.registerTypeUse(
         new TypeUse.internal(unalias(typeUse.type), typeUse.kind));
@@ skipping 95 matching lines @@
         visitList(type.optionalParameterTypes),
         type.namedParameters,
         visitList(type.namedParameterTypes));
   }
 }
 
 /// Perform unaliasing of all typedefs nested within a [ResolutionDartType].
 ResolutionDartType unalias(ResolutionDartType type) {
   return const Unaliaser().visit(type);
 }